The Post states that Mueller, who was brought on as an independent prosecutor to investigate ties between the Trump presidential campaign and Russia, is interviewing senior officials about whether Trump attempted to obstruct justice.

The story cites five officials, who spoke on the condition of anonymity. These officials claim Director of National Intelligence Daniel Coats, head of the National Security Agency Adm. Mike Rogers, and Rogers’ recently-departed deputy, Richard Ledgett, agreed to be interviewed by Mueller’s investigators as soon as this week.

In addition, officials also said investigators have been looking for any evidence of possible financial crimes among Trump associates.

According to the report, Coats, Rogers and Ledgett will be interviewed voluntarily, though it is unclear whether they will discuss their conversations with Trump in detail or if they will be instructed by the White House to invoke executive privilege.

“The FBI leak of information regarding the President is outrageous, inexcusable and illegal,” a spokesman for Trump’s legal team, Mark Corallo, said.

A spokesman for Mueller’s team also declined to comment.

Comey said in his testimony last week that, based on his understanding, Trump expected loyalty. Comey also claims that Trump asked him to ‘let go’ of an investigation of former National Security Adviser Michael Flynn.

Comey would not say in his testimony in front of the Senate Intelligence Committee whether he thought the president sought to obstruct justice, but added it would be up to special counsel Mueller “to sort that out.”

After Comey’s testimony, Trump said he was vindicated because the former FBI director confirmed the president’s claim of being informed by Comey three times that he was not under investigation.

While Comey was serving as FBI director, Trump wanted him to publicly disclose that he was not under investigation, but Comey allegedly refused. Shortly after, the Post reports that Trump spoke to Coats and Rogers about the Russia investigation.

While a sitting president is unlikely to face criminal prosecution, obstruction of justice could form the basis for impeachment. Any such step would face a significant obstacle as it would require approval by the U.S. House of Representatives, which is controlled by Trump’s fellow Republicans.